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  • December 02, 2024, 03:24:16 AM

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Author Topic: Various Performance Modifications - Add Yours  (Read 1143 times)

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Offline 89 MJ

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Various Performance Modifications - Add Yours
« on: November 02, 2024, 08:43:40 PM »
Let's talk about some of the various performance modifications people have done to their Eagles. It doesn't have to be just engine upgrades either, handling upgrades are perfect for this thread too.

Motorcraft 2150 carb - this seemed to add quite a bit of power to my car, but I did it at the same time as an HEI ignition, so I can't say which made more of a difference. I did start the car and let it run some after the carb swap and I can say that it seemed to run smoother, but I cannot speak for any power gains. Some of that difference could be the difference between a brand new carb and a 30+ year old carb that sat for 20 years and had never been rebuilt. I think this is worth doing if emissions don't matter.

HEI ignition - mine is a used unit from DUI. It came with the car, but uninstalled along with a set of Live Wires plug wires. My other experiences with HEI leads me to believe that I did gain some power with this modification, but I did do it at the same time as the carburetor, so I can't speak for sure. It took my car from not being able to spin the tires to being able to do an okay burnout. Anything I own in the future with a 258 will be getting an HEI.

Axles/Gearing - I went from the stock AMC 15 with 2.72 gears to a Chrylser 8.25 out of an XJ with 3.55 gears. It made the car way more drivable in town or on the backroads. I really didn't lose any drivability on the freeways either. The car will still run 80 mph, but its turning a lot more rpm at that speed. This is definitely the best way to get better acceleration on a budget, in my opinion.

Transfer case swap - my car came with an NP128. I swapped to an NP231J for the low range because my car does see some off road use. When I did this swap, the transfer case and the rear driveshaft length were the only two things to change. The car seriously felt like it picked up 30 horsepower after that swap. With the NP128, you could floor it from a stop and it would leisurely accelerate. With the NP231J, it will spin the tires for about 10 feet if its floored from a stop. And if you try to power brake the car to do a burnout, it will do it with ease now, whereas before the car had to work do get a tire spinning. I did it for the low range, but it definitely made the car feel way sportier too.
Does the NP129 seem to take a lot of power too?

Add-a-leaf - my factory rear springs were sagging, so I added a leaf out of another random leaf pack laying around at my house. It did make the car quite a bit stiffer in the rear, but this helped a lot with the handling too. I used some pretty heavy duty springs, so if comfort is a priority, a thinner spring would be a good choice.

Does anyone have anything to add to the list?
1986 Eagle: 258, Auto, Chrysler 8.25 rear, 3.54 gears
1989 Jeep Comanche: 4.0, AX-15, 8.8 rear, 4.10 gears
1940 Chevy PU: 350, 700R4


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